Movie people don't normally care about the finish of the iPhone they are using. And the ones that do, use a case.

I've seen all sorts of non-black (let alone matte black) iPhone rigs used for motion pictures, including white and natural titanium colors. Eg. 28 Years Later used a variety of iPhone configurations and colors.

But yeah, I'm surprised there's no black/space gray option this year. Some consumers won't buy any other color.